View Full Version : RAIL EXTRUDE = Sweep

02-28-2008, 09:20 AM
I have to admit to using LWCAD 2.5 (right now) as this is an essential set of tools for any non-organic modelling. I would say Easy Spline is also another one (one could survive without it although). So this is the problem:

I draw polyline with LWCAD tool
I convert the entity into LW type line
I Create profile in the second layer
Turn rail path into background
Start Rail Extrude command

I get this: 'rail to complex..'????

I tried with LWCAD tool without converting it into LWtype entity but Modeller does not recognize it.

How can I sweep profile when the path is not curvelinear or mathematicaly speaking quadratic line - continuous (3d) straight line:thumbsup:

02-28-2008, 09:52 PM
Just tried it and it worked. My thought is the setting for converting to a spline is set too high. When you click on curve to lwcur, open the numeric panel and see what the max freeze error is set at. The lower this number is greater amout of point will be in the spline. Increasing this number should take care of your problem.

03-03-2008, 07:51 AM
so you drew continious linar line in 3d Space (coordinates changing in x,y,z) converted it in LW line and 'swept' the profile continuously? What I have discovered is that the line conversion creates 4-6 segments. These segments although share same points do not act in union. Basically, I was able only to extrude on a single segment. That's not really a "sweep" function. Of course sweeping profile over the LW curve works. But I do not need the curve.

03-03-2008, 04:46 PM
Tried it several times and was not able to produce a multisegment spline. I was able to adjust the number of points on the spline but in each test I ended up with just the one spline.
It could be divided if you have more than one curve. If you do, use the join command to merge all the curves into one curve then covert it to a spline.
As for splines to make it a single spline, select each spline and hit shift-z. Merge polygons will merge splines. If necessary you can weld the points first.

03-04-2008, 07:55 AM
But spline is quadratic definition of the line, curvilinear. I need straight segments. Spline function is not able to produce straight segments. Effectively, what happens when I use polyline function in LWCAD is that they get converted (in order to be able to use them in rail extrude) into 2-point polygons. Conclusion: LW does not have lines (edges) but only 2-, 3-,4-,n-point polygons, splines and beziers. 2-point polygon is what we perceive as line. Am I correct?

PS There are no curves.

03-04-2008, 01:16 PM
To create a polygonal line yes, we generally do use 2 point polys in a chain. However splines are capable of producing straight lines by moving one point next or at the next point. Splines work like subpatches do, the further apart the points are the smoother the curve, while the closer they are the sharper the curve. Therefore it is possible to create a 90 degree corner box with splines by having 3 points in each corner. 1 for the corner 1 for the start of the straight line and 1 for the end of the straight line. Using the drag snap tool you can drag the start and end points on top of the corner point. then you have a sharp edged box.
In reality once the bezier tool has been dropped, the only difference between that spline and the spline tool is the corners divide the spline. For example if you create a 90 degree bend with the bezier tool you end up with 2 splines. Merging the splines will smooth out the corner. Which brings up the second way to create a sharp corner. Select the point where you want the sharp corner, then select that spline and split the spline. The disadvantage of this technique is a rail extrude will stop at the end of the first spline.

03-04-2008, 01:18 PM
PS There are no curves.
The curves I mentioned is a tool that is part of LWCad.

03-04-2008, 01:54 PM
LWcad curve - i kind of figure it in the end that this is what you meant. Thanks for the explaination of the spline term. I could never figured that one out. Too bad that curves, lines or arcs from LWCad can not be used with any standard operators (Multishift, bevel, Rail Extrude, Extend or Lathe...) since these are most common steps in modelling.
something to think about in terms of integration.

03-05-2008, 07:31 AM
Sorry I tried that with spline - a lot of work 'though. It does not work. I weld them and I get two straight spline segment not a continious one. Also RAIL BEVEL starts misbehaving after all that welding.
No clue

03-05-2008, 12:43 PM
Ok now are you using rail extrude or rail bevel, two different beasts. Rail extrude requires splines rail bevel does not. If you are using the rail bevel you should beable to kill the spline or poly and use just the points.
As for the spline after you weld the points to make it one, use shift-z to merge the two splines into one.

03-06-2008, 07:29 AM
:D I meant Rail Extrude if you misunderstood me. Anyhow I solved my problem with TAZ Pipe2. Great tool compared to Rail Extrude. However, I had no idea that you can use Rail Bevel in such way. I have to play with it again. I thought of it in more organic and interactive way. Well, thank you for opening up the possibility. I will try it tonight to recreate same things you mentioned, as I did it with TazPipe2.
It's a great tool since it accepts both splines and sequence of splines as continious entity. In numeric panel it allows you to specify # of side 4-sides=square 5-pentagon etc. Also, you can turn auto sub-patch and that way you get circular section like pipe. I still think that LW needs serious 'sweep' type operator at the level and detail like current lathe tool. thank again. Also I think Splines are no replacement for straight line segments or polylines. Yes, you showed me a trick. I did it this way: make points, ctrl-p, and add points close to control points. It works. But it is painful time consuming procedure.

03-06-2008, 08:52 AM
To be honest, I always use LWCAD lines / curves etc, then join them, then apply the profiler / engraver (can never remember which is which :p) which normally gives me what I am after.
Failing that, I use C_Worm from Pictrix which has differing control levels.

03-06-2008, 09:45 AM
Well Coklai this really helps Thanks a bunch. about the tip. In the mean time there is even better tool for FREE called BezierBridge from ArtsSphere. This is pretty much Sweep tool on one rail. Great that someone picked it up.:beerchug:

03-06-2008, 09:46 AM
C-worm is not better than TAZ Pipe or BezierBridge:)